Pharmaceutical compositions with anti-cancer activity and method for the treatment of cancer sensitive to treatment

ABSTRACT

Anti-cancer platinum complexes such as cisplatin exhibit a synergistically high level of anti-tumor activity when administered substantially simultaneously either with L-ascorbic acid, or with 5,6-O-benzylidene-L-ascorbic acid or deuterated forms thereof.

BACKGROUND OF THE INVENTION

This invention relates to pharmaceutical compositions which haveactivity as anti-cancer agents and to methods for the treatment ofcancer in patients.

Cisplatin, or cis-dichlorodiammineplatinum-II, has been usedsuccessfully for many years as a chemotherapeutic agent in the treatmentof various human solid malignant tumours. Cisplatin has the structuralformula: ##STR1## More recently, other diamino-platinum complexes havealso been proposed for use as anti-cancer drugs, for examplespiro-platinum and carbo-platinum.

Although cisplatin is widely used in medicine, nonetheless it is nottherapeutically effective in all patients, nor against all types ofsolid malignant tumours. Moreover, it has to be administered at highdosage levels such as can cause kidney damage unless special precautionsare taken.

SUMMARY OF THE INVENTION

It has now been found in accordance with the present invention thatanti-cancer platinum complexes such as cisplatin unexpectedly exhibit ahigher level of anti-tumour activity, as demonstrated by an in-vitromodel, if administered substantially simultaneously either withL-ascorbic acid or with 5,6-O-benzylidene-L-ascorbic acid (hereaftersometimes abbreviated as BASS).

Although both L-ascorbic acid and BASS are disclosed in the literatureas possessing anti-cancer properties, we have found that the enhancementof cytotoxic activity on human cancer cells which is exhibited whenthese substances are administered in conjunction with anti-cancerplatinum complexes such as cisplatin is synergistic and not merelyadditive. This result is highly surprising, more especially since oneeffect of the co-administration of an anti-cancer platinum complex suchas cisplatin with L-ascorbic acid or BASS is to reduce the up-take ofplatinum by the malignant cells, whereas the prior work on cisplatin inparticular has taught that an increase in the platinum take-up increasesthe toxicity of cisplatin.

This synergism between cisplatin and L-ascorbic acid or BASS which wehave discovered opens up the possibility of more effective cisplatintherapy and/or the use of lower dosages of cisplatin for reduced adversetoxic side-effects on the patient.

The L-ascorbic acid and 5,6-O-benzylidene-L-ascorbic acid (ie BASS) canbe used herein either as free acids or in the form of their salts withpharmaceutically acceptable cations. Moreover, the5,6-O-benzylidene-L-ascorbic acid may be deuterated at the 1-position ofthe benzylidene moiety; other work which we have done suggests that suchdeuterated BASS may have advantages in anti-cancer therapy overnon-deuterated BASS.

Thus, in accordance with one aspect, the present invention provides apharmaceutical composition useful as an anti-cancer agent, comprising asactive ingredients:

(a) an anti-cancer platinum complex, and

(b) a compound selected from L-ascorbic acid,

5,6-O-benzylidene-L-ascorbic , 5,6-O-benzyl ene-L-ascorbic aciddeuterated at the 1-position of the aldehyde group, and pharmaceuticallyacceptable salts of said acids.

The present invention also encompasses the use of a compound selectedfrom L-ascorbic acid, 5,6-O-benzylidene-L-ascorbic acid,5,6-O-benzylidene-L-ascorbic acid deuterated at the 1-position of thealdehyde group, and pharmaceutically acceptable salts of said acids, forthe manufacture of a medicament for use in a platinum complexanti-cancer therapy.

Still further, the present invention provides a method for the treatmentof cancer in a patient, which comprises simultaneously administering tosaid patient:

(i) an anti-cancer platinum complex, and

(ii) a compound selected from L-ascorbic acid,

5,6-O-benzylidene-L-ascorbic acid,5,6-O-benzylidene-L-5,6-O-benzylidene-L-ascorbic acid,5,6-O-benzylidene-L-ascorbic acid deuterated at the 1-position of thealdehyde group, and pharmaceutically acceptable salts of said acids.

When referring herein to the treatment of cancer, Applicants arereferring to the treatment of cancer sensitive to treatment with thecompositions of the present invention.

It is preferred in accordance with this invention to use cisplatin asthe anti-cancer platinum complex, and as the potentiating agenttherefor, BASS or deuterated BASS.

The deuterated 5,6-O-benzylidene-L-ascorbic acid useful herein mayadditionally be partially or completely deuterated at other positions ofits molecular structure, i.e., in addition to the deuterium atom at the1-position of the aldehyde group of the benzylidene moiety, one or morehydrogen atoms in the structure may be replaced by deuterium atoms.

The pharmaceutical composition of this invention preferably comprises afreeze-dried mixture of the active ingredients in a unit dosage formready for make-up with water for injection or other suitable infusionliquid. As is conventional with presently available freeze-driedformulations of cisplatin, the freeze-dried compositions of thisinvention may also include sodium chloride (to provide the requiredisotonicity to the infusion liquid), and/or mannitol (to help protectagainst kidney damage.

DETAILED DESCRIPTION OF THE INVENTION

The synergistic anti-cancer effect on which the present invention ispredicated is demonstrated by the experiments described below. In theseexperiments there were used L-ascorbic acid or the sodium salt of5,6-O-benzylidene-L-ascorbic acid (abbreviated as "BASS").

BIOLOGICAL MATERIALS AND METHODS USED TO DEMONSTRATE THE SYNERGISTICEFFECT

Cell culturing techniques:

Human cells of the established cell line NHIK 3025 originating from acervical carcinoma in situ (Nordbye, K., and Oftebro, R. Exp. Cell Res.,58:458, 1969), Oftebro, R., and Nordbye, K., Exp. Cell Res., 58:459-460,1969) were cultivated in Medium E2a (Puck, T.T. et al., J. Exp. Med.,106:145-165, 1957) supplemented with 20% human and 10% horse serum(Grand Island Biological Co.). The cells are grown as monolayers intissue culture flasks. The cells do not move around after they haveattached, a quality which enables the same cells to be observed in aninverted microscope for several cell generations. The cells were kept incontinuous exponential growth by frequent reculturing, i.e., everysecond and third day.

Cell Survival

For measurement of cell survival, appropriate numbers of cells wereseeded in plastic Petri dishes (φ=5 cm). The number of cells seeded intoeach dish was adjusted such that the number of surviving cells would beapproximately 150 per dish. While exponentially growing (asynchronous)cells were trypsinized before seeding, synchronized cells were seededimmediately after selection. After about 2 hours, the cells had attachedto the bottom of the dishes, and the treatment was started by replacingthe medium with medium containing the appropriate drug concentration.After the desired time of treatment, the drug-containing medium wasremoved, and fresh medium was added. The dishes were rinsed once withthe same medium as was to be added on addition or removal of drug. After10 to 12 days at 37 C in a CO₂ incubator, the cells were fixed inethanol and stained with methylene blue before the colonies werecounted.

Duration of cell cycle time:

Synchronized cell populations with a high degree of synchrony wereobtained by repeated selection of mitotic cells (Pettersen, E. O. et al,Cell Tissue Kinet., 10: 511-522, 1977). During the synchronizationprocedure, the cells were kept in Medium E2a, and the whole experimenttook place in a walk-in incubator at 37° C. Under growth conditions asused here, the NHIK 3025 cells have a medium cell-cycle time of ˜18 hr,with medium G₁, S₁ and G₂ durations of ˜7, ˜8, and ˜2.5 hr,respectively.

For detection of the drug effects on cell-cycle kinetics, the samemethods were used as described previously (Lindmo, T., and Pettersen, E.O., Cell Tissue Kinet., 12: 43-57 1979), (Pettersen, E. 0. et al, Eur.J. Cancer Clin. Oncol., 19:507-514, 1983), (Ronning, .W. et al., J.Cell. Physiol., 109:411-419, 1981). Briefly, the selected mitotic cellswere seeded into 8 tissue culture flasks (25 sq cm) 5000 cells perflask. The cells divided within 1 hr and attached as doublets to thebottom of the flasks. The cells within a delineated area of the flask(100 cells) were observed repeatedly in an inverted microscope, and thetime of entrance into mitosis, as well as the time of division, werenoted for each separate cell. Analyses of durations of mitosis wereperformed from these observations (Table).

Atomic Absorption Spectroscopy:

Analysis of cell-associated platinum was performed using a VarianSpectrAA-30 atomic absorption spectrometer fitted with a GTA-96 graphitetube atomizer. Instrument control and data acquisition were by VarianAtomic Absorption Software. Automatic background correction with amodulated deuterium lamp was utilized. Cells were loosed from flasks bytrypsin treatment and counted. Cells (2×10⁶) were added to conicalcentrifuge tubes, three replicate tubes for each drug concentration. Thetubes were centrifuged and cells were resuspended in drug-containingmedium, usually 3 ml/tube. The cells were incubated with drugs at 37° C.and held in suspension by using a rotary rack. After treatment the cellswere centrifuged and washed in phosphate-buffered NaC1 solution (NaCl,8000 mg/liter; Na₂ HPO₄ ·2H₂ O, 1150 mg/liter; KH₂ PO₄, 200 mg/liter;KCl, 200 mg/liter). The cell pellet was taken up into 100 μlconcentrated HNO₃. Following overnight oxidation of organic material,100 μl H₂ O was then added to each tube. Aliquots of 25 μl (representing250,000 cells) were then placed in a graphite tube and the atomicabsorption signal measured at 265.9 nm was registered. Platinum contentwas quantitated by running a calibration curve immediately before thesamples.

EXPERIMENT 1

In this experiment, the fraction of growing NHIK 3025 cells surviving atwo hour treatment with either 3 μM or 10 μM of cisplatin alone or incombination with various concentrations of BASS was measured. Theresults obtained are reported in Table 1 below:

                  TABLE 1                                                         ______________________________________                                                            Fraction of                                                                   Cells Surviving Treatment                                 Concentration                                                                           No        with Bass either alone or in                              of BASS   Cis-      combination with cisplatin:                               (mM)      platin    3 μM cisplatin                                                                         10 μM cisplatin                            ______________________________________                                        0         1.0       0.39 ± 0.03                                                                            0.024 ± 0.01                               2         1.06 ± 0.10                                                                          0.16 ± 0.01                                                                            0.0035 ± 0.0003                            4         1.03 ± 0.06                                                                          0.16 ± 0.01                                                                            0.0026 ± 0.0003                            10        0.79 ± 0.04                                                                          0.18 ± 0.01                                                                            0.0049 ± 0.0003                            ______________________________________                                    

From the results shown in Table 1 it will be noted that the use of BASSat all three concentrations tested significantly potentiated theactivity of the cisplatin. A BASS concentration of 4 mM can be seen tobe slightly more effective than one of 10 mM.

EXPERIMENT 2

This experiment measured the fraction of NHIK 3025 cells surviving a 2hour treatment with a combination of 3 μM cisplatin and either BASS orascorbic acid, at various concentrations. The results are given in Table2. The values given in the Table represent cell survival after thetreatment with drug combination relative to that after treatment with 3μm cisplatin alone.

                  TABLE 2                                                         ______________________________________                                        Concentration of                                                              BASS or Ascorbic                                                                            BASS +      Ascorbic Acid +                                     Acid (mM)     3 μM cisplatin                                                                         3 μM cisplatin                                   ______________________________________                                        0             1.0         1.0                                                 0.25          0.92 ± 0.04                                                                            0.92 ± 0.06                                      0.5           0.95 ± 0.05                                                                             1.0 ± 0.05                                      1             0.56 ± 0.03                                                                            0.69 ± 0.04                                      2             0.42 ± 0.03                                                                            0.37 ± 0.03                                      ______________________________________                                    

Table 2 shows relative survival values, i.e., relative to cisplatinalone, i.e., any potentiation of cisplatin toxicity by BASS or ascorbicacid would thus reduce the relative survival values to below 1.0. FromTable 2, it will be seen that the potentiating effect of BASS andascorbic acid on cisplatin were similar, but most apparent atconcentrations above 0.5 mM.

EXPERIMENT 3

This experiment measured the fraction of NHIK 3025 cells surviving a 2hour treatment with various concentrations of cisplatin either alone orin simultaneous combination with 1 mM of BASS. The results obtained aregiven in Table 3.

                  TABLE 3                                                         ______________________________________                                        Cisplatin                                                                     Concentration                                                                            Fraction of Surviving Cells:                                       (μM)    cisplatin alone                                                                            cisplatin + 1 mM BASS                                 ______________________________________                                        0          1.0          0.95 ± 0.05                                        1          0.98 ± 0.06                                                                             0.81 ± 0.05                                        2.5        0.70 ± 0.03                                                                             0.38 ± 0.02                                        5          0.24 ± 0.02                                                                             0.066 ± 0.003                                      10         0.018 ± 0.002                                                                           0.0079 ± 0.0006                                    25         0.00026 ± 0.00009                                                                       0.000029 ± 0.00001                                 ______________________________________                                    

From Table 3 it is seen that as the concentration of cisplatinincreased, so did the effectiveness of the applied combination inkilling the NHIK 3025 cells.

EXPERIMENT 4

This experiment was designed to test whether the synergistic effectswere dependent on when the two drugs (i.e., BASS and cisplatin) wereapplied to the growing NHIK 3025 cells.

In Table 4 below, the values reported represent the fraction of cellssurviving either treatment with 10 μM cisplatin alone, 2.5 mM BASS aloneor treatment with the two drugs in combination. The combined treatmentwas given either by adding the two drugs simultaneously (0 hours) oradding BASS 1 hr, 2 hrs, 3 hrs or 4 hrs after addition of cisplatin. Inall cases each individual drug was removed 2 hrs after it was added tothe cells.

                                      TABLE 4                                     __________________________________________________________________________             Hours After Start of Cisplatin Treatment                             Drug treatment                                                                         0      1    2     3    4                                             __________________________________________________________________________    2.5 mM BASS                                                                            0.95 ±                                                            alone    0.09                                                                 10 μM cisplatin                                                                     0.0062 ±                                                          alone    0.0005                                                               10 μM cisplatin +                                                                   0.00043 ±                                                                         0.003 ±                                                                         0.0069 ±                                                                         0.0074 ±                                                                        0.0053 ±                                   2.5 mM BASS                                                                            0.00002                                                                              0.0005                                                                             0.0005                                                                              0.0005                                                                             0.0005                                        __________________________________________________________________________

From Table 4 it is seen that there was an approximately 10-foldenhancement of potentiation of cisplatin when cisplatin and BASS wereadded simultaneously as compared to when BASS was added at an intervalfollowing the addition of cisplatin.

EXPERIMENT 5

This experiment measured the prolongation of the median cell-cycleduration of synchronized cells treated with either 1.5 μM of cisplatinor 2.0 mM of BASS alone, or with the two active ingredients insimultaneous combination.

The results are given in Table 5 below.

                  TABLE 5                                                         ______________________________________                                                      2.0 mM   1.5 μM                                                                              2.0 mM BASS +                                        Control                                                                              BASS     cisplatin                                                                              1.5 μM cisplatin                           ______________________________________                                        Median   19.0     21.0     41.0   58.0                                        cell cycle                                                                    duration                                                                      (hours)                                                                       Prolongation      1.11     2.15   3.05                                        (ie cell cycle                                                                duration of                                                                   treated cells                                                                 realtive to                                                                   control)                                                                      ______________________________________                                    

If the prolongation of 2.0 mM BASS+1.5 μM cisplatin had been additivethe prolongation due to the drug combination would have been(21/19)×(41/19) or 1.11×2.15=2.39. The prolongation of the combinationis 3.05 (ie 58/19) which is clearly higher than 2.39, and shows thatthere is true synergism.

EXPERIMENT 6

This experiment measured, by means of atomic absorption spectroscopy,the amount of cell-associated platinum following 2 hour treatment with30 μm cisplatin alone, or 2 hour simultaneous treatment with thecombination of 30 μM cisplatin and either BASS or ascorbic acid. Theresults are given in Table 6, in which the values given represent theamount of cell associated platinum after the combined treatment relativeto that after treatment with cisplatin alone.

                  TABLE 6                                                         ______________________________________                                        Concentration of                                                              BASS or Ascorbic BASS +      Ascorbic Acid +                                  Acid             30 μM cisplatin                                                                        30 μM cisplatin                               ______________________________________                                        0                1.0         1.0                                              1      mM        0.95 ± 0.08                                                                            0.93 ± 0.09                                   2.5    mM        0.88 ± 0.07                                                                            0.92 ± 0.06                                   5      mM        0.80 ± 0.06                                                                            0.85 ± 0.06                                   10     mM        0.76 ± 0.08                                                                            0.73 ± 0.06                                   ______________________________________                                    

Table 6 shows that both BASS and ascorbic acid reduce the relativeamount of cisplatin in cells.

Although the experiments described above clearly demonstrate that theuse of either BASS or ascorbic acid potentiate the cytotoxic propertiesof cisplatin, the explanation for the synergistic effects which havebeen observed is not known. Simple complex formation does not appear tobe the answer, since, for example, cisplatin and ascorbic acid do notreact to form a complex under the experimental conditions employed.

Although the above experiments utilized either BASS or ascorbic acid andcisplatin, it is to be expected that other derivatives of ascorbic acidwould also show similar synergism with cisplatin, or that otheranticancer platinum complexes such as spiro-platinum and carbo-platinumwould also be potentiated by, eg, BASS or ascorbic acid.

Although the above experiments utilized the sodium salt of5,6-0-benzylidene-L-ascorbic acid, it is within the scope of the presentinvention to use other pharmaceutically acceptable salts, in particularother pharmaceutically acceptable alkali and alkaline earth metal salts.The sodium salts are, however, preferred, being well-soluble in water.

Likewise, in some instances it may be preferred to use apharmaceutically acceptable salt of L-ascorbic acid rather than the freeacid itself.

The two active ingredients may be formulated together in apharmaceutical composition for simultaneous intravenous injection, oralternatively each active ingredient may be administered separately,provided that the patient receives the correct dosage of each activeingredient substantially simultaneously to ensure that the synergisticeffect is manifested in the patient.

More particularly, as the accepted route of administration for cisplatinis by intravenous injection as shown in the art of cancer chemotherapy,the BASS or L-ascorbic acid ma be given either orally to immediatelyprecede, or simultaneously with, cisplatin administration. For oraladministration 5,6-O-benzylidene-L-ascorbic acid or salt thereof, or ofa deuterated aldehyde derivative, will be in the range of 10 to 75 mgper kg of body weight up to twice daily, with the anti-cancer platinumcompound being given during one of the BASS treatment periods.Acceptable ranges for L-ascorbic acid, or salt thereof, will be from 10to 100 mg per kg of body weight up to twice daily. For intravenousinfusion or injection, BASS or ascorbic acid, or an acceptable saltthereof, may be given simultaneously with but independently of theplatinum treatment, or simultaneously with and in admixture with theanti-cancer platinum compound. The suitable ranges for5,6-O-benzylidene-L-ascorbic acid or alkaline earth salts thereof, or ofthe deuterated compounds, will be 10 to 75 mg per kg of body weight upto twice daily with the anti-cancer platinum compound being administeredduring one of the BASS treatment periods. Ascorbic acid as sodiumascorbate or buffered with sodium carbonate will be present in the drugcombination regimen at physiologically acceptable levels, normallyapproximately 10 to 100 mg per kg of body weight up to twice daily withthe anti-cancer platinum compound being administered during one theascorbic acid treatment periods. The dosage of cisplatin or otherplatinum complex is suitably within the range of 0.5 to 2 mg per kg ofbody weight for cisplatin, or from 0.5 to 50 mg per kg of body weightfor other anti-cancer platinum compounds, for example carboplatinum,either once every 3-4 weeks as a single dose, or daily from 1 to 5 daysas split dosages such that the total platinum dosage does not exceed theabove ranges.

Thus, for example, for an adult patient, 0.15 g to 1.5 g of BASS orL-ascorbic acid will preferably be given orally per day in combinationwith up to 150 mg of cisplatin intravenously. For infusion, an adultpatient preferably would receive 0.15 g to 1.5 g of BASS or L-ascorbicacid, either in combination with 50 to 150 mg of cisplatin or singly, inthe latter case the cisplatin then also being given singly butsubstantially simultaneously.

Pharmaceutical compositions containing both the active ingredients ofthe present invention for intravenous infusion or injection may beformulated in numerous ways well known to those skilled in the art withpharmaceutically acceptable excipients or carriers for injection orinfusion. As indicated above, freeze-dried mixtures of the activeingredients in a unit dosage form, prepared by conventional methods,preferably are made up with water for injection or other suitableinfusion liquid at the time of administration.

The content of the active ingredients in the pharmaceutical compositionsaccording to this invention may vary quite widely, depending on therequired dosage. For administration, the content of5,6-O-benzylidene-L-ascorbic acid or L-ascorbic acid, orpharmaceutically acceptable salt thereof, will usually be about 10:1 to1000:1 by weight, with respect to the anti-cancer platinum complexpresent in the composition. Corresponding amounts will apply for thedeuterated BASS compounds. Preferably, the compositions will comprisefrom 5 mg to 500 mg of the anti-cancer platinum complex, and from 100 mgto 10,000 mg of the ascorbic acid or ascorbate. Mannitol and/or sodiumchloride may preferably be included in amounts conventional forcisplatin preparations.

Physiological pH of injectables or infusion drug combinations will beestablished by inclusion of buffering agents as is known in thepharmaceutical art.

For oral administration of L-ascorbic acid or BASS, the compositionscontaining these active ingredients may be presented in the form oftablets, capsules, granules or powders, in accordance with proceduresknown in the pharmaceutical formulation art.

We claim:
 1. A pharmaceutical composition useful as an agent suitablefor the treatment of a cancer sensitive to the composition, saidcomposition comprising an anti-cancer effective amount of a synergisticcombination of(i) cisplatin, and (ii) 5,6-O-benzylidene-L-ascorbic aciddeuterated in the 1 position of the aldehyde group of the benzylidenemoiety or a pharmaceutically acceptable salt thereofand apharmaceutically acceptable carrier therefor.
 2. A composition accordingto claim 1 wherein said pharmaceutically acceptable salt is selectedfrom alkali metal and alkaline earth metal salts.
 3. A compositionaccording to claim 1 or claim 2 wherein the combination of ingredients(i) and (ii) is in freeze dried form.
 4. A composition according toclaim 3 comprising from 5 mg to 500 mg by weight of (i) and from 100 mgto 10,000 mg of (ii).
 5. A composition according to claim 4 which alsocontains mannitol and sodium chloride.
 6. A method for the treatment ofcancer in a patient which comprises administering to said patent ananti-cancer effective amount of a synergistic combination of(i)cisplatin, and p1 (ii) 5,6-O-benzylidene-L-ascorbic acid deuterated inthe 1-position of the aldehyde group of the benzylidene moiety or apharmaceutically acceptable salt thereof,the cancer being one sensitiveto the combination, the administration of (i) being by injection and theadministration of (ii) being by injection or orally.
 7. A methodaccording to claim 6 wherein (i) and (ii) are administeredsimultaneously by injection.
 8. A method according to claim 6 wherein(i) and (ii) are separately administered.
 9. A method according to anyone of claims 6, 7 or 8 wherein (i) is administered by infusion in anamount of from 0.05 to 50 mg per kg of body weight of the patient perday and in conjunction therewith (ii) is administered in an amount offrom 10 to 100 per kg of body weight of the patient.